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Quantum information processing using nuclear spin orientation in a single quantum dot

使用单个量子点中的核自旋取向进行量子信息处理

基本信息

批准号：
18360001
负责人：
MUTO Shunichi
金额：
$ 9.59万
依托单位：
Hokkaido University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2006
资助国家：
日本
起止时间：
2006 至 2007
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-18360001/
关键词：
nuclear spin electron spin quantum memory hysteresis quantum bit single quantum dot exciton hyperfine interaction 光配向量子情報

项目摘要

In this project, we did a feasibility study of memory applications of quantum mechanically superposed states of an ensemble of nuclear spins. In other words, we tried to clarify the possibility of quantum information storage using quantum bit (qubit) conversion of a photon to an ensemble of nuclear spins mediated by a single electron spin through hyperfine interaction. For this purpose, we had to realize the situation where energy at the flip-flop of electron and nuclear spins is conserved, that is, the cancellation of external magnetic field and the effective nuclear field.In 2006, we studied the formation of nuclear field as functions of intensity and degree of circular polarization of excitation light on a single InAlAs/GaAs quantum dot (QD). As a result, we observed hysteresis in the nuclear magnetic field as a function of intensity of the excitation light which is circularly polarized. We can interpret this phenomenon as a nuclear spin switching and we concluded that the cancellation of external magnetic field and the effective nuclear field was realized. This is a condition necessary for the electron nuclear spin qubit conversion.In 2007, we advanced our study to include the magnetic field dependence. Upon increasing field the nuclear field increased to a certain threshold value above which the nuclear field discontinuously decreased. Comparison with theoretical calculations tells us that the nuclear field completely cancelled the external magnetic field. Unfortunately, however, this nuclear field is determined by the balance of the formation and destruction of nuclear spin polarization, and is not indicating the perfect polarization or the nuclear dark state both of which can be used for the electron nuclear spin qubit conversion. This shows that the current status of InAlAs QD is not suitable for the qubit conversion and either enhancement of nuclear spin formation or reduction of spin deformation is needed.

在这个项目中，我们对核自旋系综的量子力学叠加态的存储应用进行了可行性研究。换句话说，我们试图阐明量子信息存储的可能性，通过超精细相互作用，将一个光子转化为单电子自旋介导的核自旋系综。为此，我们必须认识到电子和核自旋翻转的能量守恒的情况，即外部磁场和有效核场的抵消。2006年，我们研究了单个InAlAs/GaAs量子点(QD)上核场的形成与激发光的强度和圆偏振度的函数关系。因此，我们观察到核磁场中的滞后现象是圆偏振激发光强度的函数。我们可以将这一现象解释为原子核的自旋转换，从而实现了外加磁场和有效核场的抵消。这是电子核自旋量子比特转换的必要条件。2007年，我们进一步研究了磁场的依赖关系。随着电场的增加，核场增加到一定的阈值，超过该阈值，核场不连续地减小。与理论计算的比较表明，核场完全抵消了外加磁场。然而，不幸的是，这个核场是由核自旋极化的形成和破坏的平衡决定的，而不是表示完全极化或核暗状态，这两者都可以用于电子的核自旋量子比特转换。这表明，InAlAs量子点的现状不适合于量子比特转换，需要加强核自旋形成或减少自旋形变。